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Design of Compact Multi-Path Thomson Scattering Diagnostic with Signal Delay System in Heliotron J

Dechuan QIU, Takashi MINAMI¹⁾, Takuya NISHIDE, Masahiro MIYOSHI, Yuta YAMANAKA, Shinichiro KADO¹⁾, Shinsuke OHSHIMA¹⁾, Kazunobu NAGASAKI¹⁾, Hiroyuki OKADA¹⁾, Shinji KOBAYASHI¹⁾, Tohru MIZUUCHI¹⁾, Shigeru KONOSHIMA¹⁾ and Ryo YASUHARA²⁾

Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan

1)

Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan

2)

National Institute for Fusion Science, 322-6 Oroshi-cho, Toki, Gifu 509-5292, Japan

(Received 6 January 2020 / Accepted 18 May 2020 / Published 15 July 2020)

Abstract

A new design of a multi-path Thomson scattering system with signal delay function based on a polarization control technique is proposed on Heliotron J to deal with the overlapping phenomenon of scattered light signals. By operating double Pockels cells to control the injection timing of the laser beam into plasma, the adjacent scattering signals corresponding to opposite incident laser beams are expected to be separated to some extent for better analyzing the anisotropic temperature. Two image relay systems are also designed and integrated into the system to suppress the reduction of the laser beam power during multi-path propagation. Estimations are made on residual power of laser and separation degree of adjacent scattered light signals to reveal the feasibility of this new design. This design is instructive for fusion devices that desire anisotropic measurement but also face limitations of less setting optical path.

Copyright (c) 2020 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

multi-path Thomson scattering, anisotropic velocity distribution, Pockels cell

DOI: 10.1585/pfr.15.2401044

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